Patent GB-114422-A (GB)
Title: Improvements in Automatic Telephone Systems.
IPC: H04Q3/62
Filed: 1918-02-25
Abstract: 114,422. Automatic Telephone Manufacturing Co., (Assignees of Jacobsen, E.). March 19, 1917, [Convention date]. Automatic exchange systems; metering systems.--In a system particularly suitable for private installations with connexions to a public automatic exchange, switches are used having the sets of line terminals arranged in a single level. The parties are numbered 1 - - 9, 01 - - 09, 001 - - 009, and so on, each tenth set of terminals being dead, so that parties in the first group can be selected by a single set of impulses, parties in the second, third, and further groups being selected by two, three, or more sets of impulses, of which the first, second, &c. sets consist of ten impulses, the wipers momentarily resting upon the dead sets of terminals. Certain sets of terminals are reserved for trunks to the main exchange, the arrangement being such that if the first of such trunks is in use, the switch automatically finds the first idle trunk, or if they are all in use, comes to rest on the last trunk, and transmits a busy signal to the calling party. The trunks to the main exchange are arranged for two-way working, and terminate at the branch exchange in a combined connector-repeater, acting as a repeater for outgoing calls and as a connector for incoming calls. The private lines are not provided with cut-off relays, so that a called party may operate his switch to bring a third party into the talking connexion, and similarly the third party may call in a fourth party, and so on. Connexion of substation A, Fig. 2, to substation A<1>, Fig. 1, at the same private exchange. When the party A removes his receiver, the relays 15, 17 are energized over the loop circuit; relay 17 energizes without effect but relay 15 energizes a slow-release relay 16, which marks the calling- line busy by grounding wire 28 and prepares the circuit of the stepping-magnet 20. The party A then transmits four impulses to call party A'. The movement of the dial from its normal position shifts the springs S, opening the loop circuit and earthing the lead 11 through the impulsesender C D, thus de-energizing relay 17 while relay 15 remains energized over lead 11. The interruptions of the circuit of relay 15 are repeated to the motor magnet 20 over a circuit from ground G<4>, armatures 39, 41, 43, 54, 55 to the magnet 20 and battery, thus moving the wipers 21 - - 24 to the terminals 60 - - 63 of the wanted line as shown in Fig. 2. When the dial returns to normal, springs S complete again the loop circuit through relay 17, and, if the selected line is idle, a circuit is closed for the switching-relay 19 from ground G', upper winding of the busy transformer 36, armature 47, lower windings of relays 17, 19, armature 51, test wiper 22, lead 28<1>, Fig. 1, of subscriber A<1>, and resistance 58 to battery B<4>. Relay 19 locks up over its upper winding, and (1) opens at armature 51 its original energizing circuit, (2) connects the test wiper 22 to earth G<4> over armature 51, thus marking the line A<1> busy, (3) disconnects the stepping-magnet 20, and (4) completes the talking circuit at its armatures 53, 56. To ring up the wanted party, the party A depresses his ringing-push PB, thereby opening the loop circuit so as again to de-energize relay 17, which completes a circuit from the ringing- lead 33, over armatures 40, 46, 49, 53, wiper 24, lead 12', and ringer 5' to earth. When he removes his receiver, the called party is supplied with microphone current from the relays 15<1>, 17' of his switch C', in exactly the same way as the calling party is from the relays 15, 17. The talking circuit includes the condenser 57 in switch C and the condenser 57<1> in switch C<1> which are on opposite sides of the connexion. When the calling party replaces his receiver, the relays 15, 16, 17, 19 de-energize, and a circuit is completed for the stepping-magnet 20 to restore the switch to normal, this circuit passing from ground G<4> over armatures 41, 43, fourth wiper 21, terminal 60, lead 31, armature 44, interrupter armature of stepping-magnet 20, armature 55, and magnet 20 to battery. The intermittent operation of magnet 20 rotates the wipers until they reach the first set of terminals, which are dead, the circuit being opened at wiper 21. The fourth terminals, such as 60, of each set belonging to private lines are connected together as shown in Fig. 2 and are not multipled to similar contacts of other switches. The fourth terminals, such as 70, 74, of each set belonging to trunks to the main exchange are connected differently as described later. The relay 18, Fig. 2, is not energized during a connexion between two parties on the private exchange. If the wanted party is busy, his test terminal 61 is earthed, so that when the line relay 17 energizes, upon the return of the dial to normal, the relay 19 is not energized. A busy signal is given to the calling party by the connexion of the upper winding of the busy transformer 36 through the lower windings of relay 17, 19 to the earth on the busy test terminal 61. As the upper winding of relay 17 is inductively related to the lower winding, a busy tone is produced in the receiver of the calling party. If the busy called party becomes idle before the calling party hangs up, the connexion will be completed. If the wanted line is busy, the calling party may operate his dial again to make a further call, without replacing his receiver. If the wanted party is in the second, third, or later groups numbered as 01 - - 09, 001 - - 009, &c., the calling party transmits one or more sets of ten impulses which bring the wipers on to the sets of dead terminals previously mentioned, and then a further set of impulses corresponding to the last digit of the wanted line. Connexion of substation A, Fig. 2, to idle trunk 110, 111, Fig. 3, to main exchange. In the system described, the two first sets of terminals on the subscriber's connectors are allotted to trunks to the main exchange, and a subscriber, wishing to call a party on the main exchange is instructed to prefix the digit 1 to the directory number of the wanted line. In response to this single impulse, the connector C acts in the manner previously described to engage its wipers 21 - - 24 with the terminal 70 - - 73 of the first exchange trunk. If this trunk is busy, its test terminal 71 is earthed, so that when the relay 17 energizes upon the return of the dial to its normal position, the switching-relay 19 is not energized, but a circuit is completed to rotate the wipers to find an idle trunk, this circuit passing from the stepping-magnet 20 through the armatures 55, interrupting-armature of magnet 20, wire 29 (which is connected to the fourth terminals, such as 70, of all trunks to the main exchange) terminals 70, wiper 21, armature 45, and test wiper 22 to the earthed test terminal 71. When an idle trunk is found, this circuit is opened and the switching- relay 19 is energized as previously described, with the additional result, occurring only when connexion is established with a trunk line, that the relay 18 is energized over a circuit which includes the magnet 20, relay 18, interrupter contact of magnet 20, resistance 82, wire 30, terminal 74, wiper 21, and armatures 45, 51, 42 to ground' at G<2>. The resistance of this circuit is such that the magnet 20 does not energize, but the relay 18 locks up and disconnects the line relays 15, 17 and the condenser 57, extending the calling line direct to the wipers 23, 24, thereby energizing the line relay 102 of the repeater-connector E, Fig. 3. The relay 102 energizes the usual slowrelease relay 103, which earths wire 128 so as to mark the trunk 110, 111 busy and maintain a holding-circuit for the relays 18, 19 of the connector C after the relay 16 has de-energized. If all the trunks to the main exchange had been busy, the wipers of the connector C would have remained at rest upon the terminals 74 - - 77 of the last trunk, the fourth terminal 74 of which is connected by a separate wire 30 and resistance 82 to the interrupter armature of the stepping-magnet 20. The resistance 82 is such that the magnet 22 cannot energize in series! with it, so that the wipers come to rest on the terminals of the last trunk, irrespective of whether this is busy or idle. If the last trunk is busy, the relay 19 is not energized and a busy signal is given to the calling party as before. Returning now to the repeater-connector E, Fig. 3, the line relay 102 is energized over the calling line and the release relay 103 bridges the upper winding of a relay 105 across the trunk 110, 111, thus causing a line switch at the main exchange to connect the trunk to an idle selector as described in Specification 1419/10. Further sets of selecting-impulses sent by the calling party are repeated by the relay 102 to the main exchange, a slow-release relay 104 removing the resistance of the relay 105 from the trunk circuit during the repetition of impulses. The talking circuit is shown in heavy lines, microphone current being supplied to the calling party through relays 102 and inductance 100, which are bridged across the talking circuit on the local side of the condensers 153, 154. Release is effected when the calling party replaces his receiver, relays 102, 103 de-energizing in succession. On the release of relay 19, the stepping-magnet 20 is energized over the circuit previously traced, except that it includes initially terminal 74, wire 30, -and a resting contact of armature 44. Connexion from main exchange over trunk 110, 111, Fig. 3, to substation A', Fig. 1. When the trunk 110, 111 is taken into use at the main exchange, relay 106 is energized over the trunk and closes a circuit for the release relay 107, which earths the test lead 128 to mark the trunk busy to the local connectors. The selecting-impulses sent over the trunk are repeated by relay 106 to the stepping-magnet 120, whic